1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus, image processing apparatus, and program which perform subtraction processing between images before and after the injection of a contrast medium.
2. Description of the Related Art
In performing DSA (Digital Subtraction Angiography) examination of an abdominal region, the patient is basically forced to temporarily hold his/her breath. However, normal DSA cannot be performed on a patient who cannot hold his/her breath, e.g., an elderly person, an infant, or an unconscious patient. Under the circumstances, there has been proposed a method of acquiring a larger number of mask images than that obtained by normal DSA, and selecting an optimal mask image, for each contrast image, which is similar in tissue movement to the contrast image from the acquired mask images, thereby obtaining a DSA image with only a blood vessel being enhanced while suppressing motion artifacts caused by the respiration of the patient (see Jpn. Pat. Appln. KOKAI Publication No. 2004-112469).
This method gives consideration to a region with much movement in determining an optimal mask image, and determines an optimal mask by comparison with a contrast image upon localization to the region.
However, a great shift may sometimes occur. This shift occurs because this method makes a blood vessel coincide with the bone structure of a mask image so as to reduce the influence of a signal based on the blood vessel which does not exist in the mask image. See Jpn. Pat. Appln. KOKAI Publication No. 2004-112469.